Conventionally, it is known that the HEMT having the metal insulator semiconductor (MIS) structure has a gate field plate that is defined integrally with a gate electrode in order to alleviate the concentration of an electric field on an end of the gate electrode. On the other hand, as another technique for alleviating the electric field concentration, it is proposed to define a source field plate on a side of the gate electrode, the source field plate being electrically connected to the source electrode.